A main characteristic of a modern telecommunication network is its ability to provide different services. One efficient way of providing said services is to logically separate the resources of a physical network--resource separation (see FIG. 1). On top of a physical network PN there is established a number of logical networks LN, also referred to as logical or virtual subnetworks, each of which comprises nodes N and logical links LL interconnecting the nodes. Each logical network forms a logical view of parts of the physical network or of the complete physical network. In particular, a first logical network LN1 comprises one view of parts of the physical network and a second logical network LN2 comprises another view, different from that of the first logical network. The logical links of the various logical networks share the capacities of physical links present in said physical network.
A physical network comprises switches S (physical nodes) or equivalents, physical links interconnecting said switches, and various auxiliary devices. A physical link utilizes transmission equipment, such as fiber optic conductors, coaxial cables or radio links. In general, physical links are grouped into trunk groups TG which extend between said switches. There are access points to the physical network, to which access points access units, such as telephone sets and computer modems, are connected. Each physical link has limited transmission capacity.
FIG. 2 is a simple schematic drawing explaining the relationship between physical links, logical links and also routes. A simple underlying physical network with physical switches S and trunk groups TG, i.e. physical links, interconnecting the switches is illustrated. On top of this physical network a number of logical networks are established, only one of which is shown in the drawing. The logical networks can be established by a network manager, a network operator or other organization. In our Swedish Patent Application 9403035-0, incorporated herein by reference, there is described a method of creating and configuring logical networks. The single logical network shown comprises logical nodes N1, N2, N3 corresponding to physical switches S1, S2 and S3 respectively. Further, the logical network comprises logical links LL interconnecting the logical nodes N1-N3. A physical link is logically subdivided into one or more logical links, each logical link having an individual traffic capacity referred to as logical link capacity. It is important to note that each logical link may use more than one physical link or trunk group. To each node in each logical network there is usually associated a routing table, which is used to route a connection from node to node in the particular logical network starting from the node associated with the terminal that originates the connection and ending at the node associated with the terminal which terminates said connection. Said nodes together form an origin-destination pair. A node pair with two routes is also illustrated. One of the routes is a direct route DR while the other one is an alternative route AR. In the figures, the links and the routes may be interpreted as being bidirectional.
In order to avoid misconceptions the following definitions will be used: A route is a subset of logical links which belong to the same logical network, i e. a route have to live in a single logical network. Note that it can be an arbitrary subset that Is not necessarily a path in the graph theoretic sense. Nevertheless, for practical purposes, routes are typically conceived as simple paths. The conception of a route is used to define the way a connection follows between nodes in a logical network. A node pair in a logical network, the nodes of which are associated with access points, is called an origin-destination (O-D) pair. In general, all node pairs in a logical network are not O-D pairs, but instead some nodes in a logical network may be intermediate nodes to which no access points are associated. A logical link is a subset of physical links.
Information, such as voice, video and data, is transported In logical networks by means of different bearer services. Examples of bearer services are STM 64 (Synchronous Transmission Mode with standard 64 kbit/s), STM 2 Mb (Synchronous Transmission Mode with 2 Mbit/s) and ATM (Asynchronous Transfer Mode). From a service network, such as PSTN (Public Switched Telephone Network) and B-ISDN (Broadband Integrated Services Digital Network) a request is sent to a logical network that a connection should be set up in the corresponding logical network.
Although the physical network is given, it is necessary to decide how to establish logical networks on top of the physical network and how to distribute or partition said physical network resources among logical networks by subdividing physical link capacities into logical link capacities associated with said logical networks. Since the logical networks share the same given physical capacities, there is a trade-off between their quality: GoS (Grade of Service) parameters, call blocking probabilities etc. can be improved in one of the logical networks only at the price of degrading the quality in other logical networks. It is a highly non-trivial task to find the partitioning of resources so as to optimize the overall network performance, in particular when considering a large and complex network. Furthermore, the network performance is also affected by the distribution of offered traffic load among the routes which can realize communication even within a single network. It is the management and dimensioning of a resource separated network to which the present invention is directed.